Why not a PR with a sonosub? (1 Viewer)

[Jay C]

The search on this site is nearly never available when I dream these questions up, so here goes. I have made the rounds to anyone and everyone's site with regards to a sonosub. everyone uses a port design. Whereas in the box built community (he15 comes to mind) they use passive radiators. I still have not grasped what a PR does different over a port, but why not use a PR instead? Is it cost? Tuning? Size? I have read those sites that describe the different designs (like the Lambda whitepapers, subwoofer cookbook, etc...) but perhaps someone could fill me in a bit more.
Thanks in advance,
Jay

 

[Kyle Richardson]

Passive radiators cannot be mounted in a horizontal position so they cannot be used in a sonotube that is in it's "traditional" position of beind on end. If the sonotube is layed down, however, it will be just fine.
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[Shade Watson]

Kyle,
My Velodyne VA-1012X has a horizontally mounted PR.

 

[Julian Data]

Velodyne doesn't use the "typical" PR constructing. That's I am thinking.
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[GaryM]

The other problem is that the driver mounting area in a Sonotube is relatively sparse, only the end caps. Add to this the fact that PR's need to be larger than the driven cones (or multiple PR's used), plus the required amp mounting area, and you rapidly run out of endcap real estate.
Cube subwoofers often have the PR's mounted at right angles to the box, and dual-PR designs typically place them on opposite faces of the box (to cancel mechanical forces), with downward facing drivers. This may also be due to real estate problems, since the PR subwoofer for a given tuning can have a somewhat smaller box than a vented design (remember that the volume occupied by the vent tube itself gets large as the vent tube increases in diameter and length).
There comes a point when building a bigger and bigger subwoofer, where the PR approach is simply more desireable because it gives more low frequency output in a smaller volume. Sonotubes become very difficult to use when they exceed 60" in length or 24" in diameter, while the larger but rectangular shaped boxes continue to fit through normal doors until you get really outrageous about box volume.
Gary